Remove redundant code from bl1_plat_helpers.S

Remove redundant code in plat_secondary_cold_boot_setup() in
plat/fvp/aarch64/bl1_plat_helpers.S.

Fixes ARM-software/tf-issues#136

Change-Id: I98c0a46d95cfea33125e34e609c83dc2c97cd86e
Merge pull request #44 from danh-arm/dh/tf-issues#136

Remove redundant code from bl1_plat_helpers.S